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Mario Rojo - One of the best experts on this subject based on the ideXlab platform.
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Trace Element Geochemistry of magnetite from the Cerro Negro Norte iron oxide−apatite deposit, northern Chile
Mineralium Deposita, 2019Co-Authors: Eduardo Salazar, M Leisen, Gisella Palma, Rurik Romero, Martin Reich, Fernando Barra, Adam Simon, Mario RojoAbstract:Kiruna-type iron oxide−apatite (IOA) deposits constitute an important source of iron and phosphorus, and potentially of rare earth Elements (REE). However, the origin of IOA deposits is still a matter of debate with models that range from a purely magmatic origin by liquid immiscibility to replacement of host rocks by hydrothermal fluids from different sources. In order to better constrain the origin of Andean IOA deposits, we focused on the Cretaceous Cerro Negro Norte deposit located in the Chilean Iron Belt, northern Chile. The Cerro Negro Norte magnetite ore is hosted in andesitic rocks and is spatially and genetically associated with a diorite intrusion. Our results show that the deposit is characterized by three main mineralization/alteration episodes: an early Fe–oxide event with magnetite and actinolite followed by four stages that comprise the main hydrothermal event (hydrothermal magnetite + actinolite; calcic–sodic alteration + sulfides; quartz–tourmaline and propylitic alteration) and a minor supergene event. Based on textural and chemical characteristics, four different types of magnetite are recognized at Cerro Negro Norte: type I, represented by high-temperature (~ 500 °C) magnetite cores with amphibole, pyroxene, and minor Ti–Fe oxide inclusions; type II, an inclusion-free magnetite, usually surrounding type I magnetite cores; type III corresponds to an inclusion-free magnetite with chemical zoning formed under moderate temperatures; and type IV magnetite contains abundant inclusions and is related to low-temperature (~ 250 °C) hydrothermal veinlets. Electron probe and laser ablation ICP-MS analyses of the four magnetite types show that the incorporation of Al, Mn, Ti, and V into the magnetite structure is controlled by temperature. Vanadium and Ga concentrations are relatively constant within each magnetite type, but are statistically different among magnetite types, suggesting that both Elements could be used to discriminate between magmatic and hydrothermal magnetite. However, our results show that the use of Elemental discrimination diagrams should be coupled with detailed textural studies in order to identify superimposed metasomatic events and evaluate the impact of inclusions on the interpretation of microanalytical data. The presence of a distinct textural and chemical variation between magnetite types in Cerro Negro Norte is explained by a transition from high- to low-temperature magmatic-hydrothermal conditions. The microanalytical data of magnetite presented here, coupled with new δ^34S data for pyrite (− 0.5 to + 4.3‰) and U–Pb ages of the diorite (129.6 ± 1.0 Ma), are indicative of a genetic connection between the diorite intrusion and the magnetite mineralization, supporting a magmatic-hydrothermal flotation model to explain the origin of Kiruna-type deposits in the Coastal Cordillera of northern Chile.
Troy Rasbury - One of the best experts on this subject based on the ideXlab platform.
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unravelling the genesis of young continental arc shoshonites in the talamanca cordillera costa rica
Lithos, 2021Co-Authors: Aristides Alfaro, Esteban Gazel, William M White, Brian R Jicha, Troy RasburyAbstract:Abstract Six to five Myr. old continental-arc shoshonites and other high-K igneous rocks crop out among the summits of the Talamanca Cordillera, Central America. These rocks fill a previously assumed volcanic gap in eastern Costa Rica, showing that the Late Miocene-Pliocene magmatic arc was almost continuous along the current Talamanca Cordillera. Their Trace Element compositions (e.g., Sr ~ 1700 ppm at Rb ~ 120 ppm concentrations) together with fractional crystallization modeling, and isotopic signatures suggest a genesis related to subduction processes rather than lower crustal melting. Here we present a comprehensive geochemical study that integrates Monte Carlo simulations of Trace Element Geochemistry and isotopic evidence in order to explain the origin of these highly enriched igneous rocks. The Trace Element budget of the Talamanca arc rocks requires the input of an incompatible Element-enriched component, similar in composition to the Cocos Island Province (Pacific Ocean). We interpret the presence of this component to be the result of slab melting of subducted seamounts. Our model suggests that, in the southern Central American, contribution of OIB-related seamounts is a critical step for the generation of continental crust-like rock compositions.
Eduardo Salazar - One of the best experts on this subject based on the ideXlab platform.
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Trace Element Geochemistry of magnetite from the Cerro Negro Norte iron oxide−apatite deposit, northern Chile
Mineralium Deposita, 2019Co-Authors: Eduardo Salazar, M Leisen, Gisella Palma, Rurik Romero, Martin Reich, Fernando Barra, Adam Simon, Mario RojoAbstract:Kiruna-type iron oxide−apatite (IOA) deposits constitute an important source of iron and phosphorus, and potentially of rare earth Elements (REE). However, the origin of IOA deposits is still a matter of debate with models that range from a purely magmatic origin by liquid immiscibility to replacement of host rocks by hydrothermal fluids from different sources. In order to better constrain the origin of Andean IOA deposits, we focused on the Cretaceous Cerro Negro Norte deposit located in the Chilean Iron Belt, northern Chile. The Cerro Negro Norte magnetite ore is hosted in andesitic rocks and is spatially and genetically associated with a diorite intrusion. Our results show that the deposit is characterized by three main mineralization/alteration episodes: an early Fe–oxide event with magnetite and actinolite followed by four stages that comprise the main hydrothermal event (hydrothermal magnetite + actinolite; calcic–sodic alteration + sulfides; quartz–tourmaline and propylitic alteration) and a minor supergene event. Based on textural and chemical characteristics, four different types of magnetite are recognized at Cerro Negro Norte: type I, represented by high-temperature (~ 500 °C) magnetite cores with amphibole, pyroxene, and minor Ti–Fe oxide inclusions; type II, an inclusion-free magnetite, usually surrounding type I magnetite cores; type III corresponds to an inclusion-free magnetite with chemical zoning formed under moderate temperatures; and type IV magnetite contains abundant inclusions and is related to low-temperature (~ 250 °C) hydrothermal veinlets. Electron probe and laser ablation ICP-MS analyses of the four magnetite types show that the incorporation of Al, Mn, Ti, and V into the magnetite structure is controlled by temperature. Vanadium and Ga concentrations are relatively constant within each magnetite type, but are statistically different among magnetite types, suggesting that both Elements could be used to discriminate between magmatic and hydrothermal magnetite. However, our results show that the use of Elemental discrimination diagrams should be coupled with detailed textural studies in order to identify superimposed metasomatic events and evaluate the impact of inclusions on the interpretation of microanalytical data. The presence of a distinct textural and chemical variation between magnetite types in Cerro Negro Norte is explained by a transition from high- to low-temperature magmatic-hydrothermal conditions. The microanalytical data of magnetite presented here, coupled with new δ^34S data for pyrite (− 0.5 to + 4.3‰) and U–Pb ages of the diorite (129.6 ± 1.0 Ma), are indicative of a genetic connection between the diorite intrusion and the magnetite mineralization, supporting a magmatic-hydrothermal flotation model to explain the origin of Kiruna-type deposits in the Coastal Cordillera of northern Chile.
Aristides Alfaro - One of the best experts on this subject based on the ideXlab platform.
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unravelling the genesis of young continental arc shoshonites in the talamanca cordillera costa rica
Lithos, 2021Co-Authors: Aristides Alfaro, Esteban Gazel, William M White, Brian R Jicha, Troy RasburyAbstract:Abstract Six to five Myr. old continental-arc shoshonites and other high-K igneous rocks crop out among the summits of the Talamanca Cordillera, Central America. These rocks fill a previously assumed volcanic gap in eastern Costa Rica, showing that the Late Miocene-Pliocene magmatic arc was almost continuous along the current Talamanca Cordillera. Their Trace Element compositions (e.g., Sr ~ 1700 ppm at Rb ~ 120 ppm concentrations) together with fractional crystallization modeling, and isotopic signatures suggest a genesis related to subduction processes rather than lower crustal melting. Here we present a comprehensive geochemical study that integrates Monte Carlo simulations of Trace Element Geochemistry and isotopic evidence in order to explain the origin of these highly enriched igneous rocks. The Trace Element budget of the Talamanca arc rocks requires the input of an incompatible Element-enriched component, similar in composition to the Cocos Island Province (Pacific Ocean). We interpret the presence of this component to be the result of slab melting of subducted seamounts. Our model suggests that, in the southern Central American, contribution of OIB-related seamounts is a critical step for the generation of continental crust-like rock compositions.
M Leisen - One of the best experts on this subject based on the ideXlab platform.
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Trace Element Geochemistry of magnetite from the Cerro Negro Norte iron oxide−apatite deposit, northern Chile
Mineralium Deposita, 2019Co-Authors: Eduardo Salazar, M Leisen, Gisella Palma, Rurik Romero, Martin Reich, Fernando Barra, Adam Simon, Mario RojoAbstract:Kiruna-type iron oxide−apatite (IOA) deposits constitute an important source of iron and phosphorus, and potentially of rare earth Elements (REE). However, the origin of IOA deposits is still a matter of debate with models that range from a purely magmatic origin by liquid immiscibility to replacement of host rocks by hydrothermal fluids from different sources. In order to better constrain the origin of Andean IOA deposits, we focused on the Cretaceous Cerro Negro Norte deposit located in the Chilean Iron Belt, northern Chile. The Cerro Negro Norte magnetite ore is hosted in andesitic rocks and is spatially and genetically associated with a diorite intrusion. Our results show that the deposit is characterized by three main mineralization/alteration episodes: an early Fe–oxide event with magnetite and actinolite followed by four stages that comprise the main hydrothermal event (hydrothermal magnetite + actinolite; calcic–sodic alteration + sulfides; quartz–tourmaline and propylitic alteration) and a minor supergene event. Based on textural and chemical characteristics, four different types of magnetite are recognized at Cerro Negro Norte: type I, represented by high-temperature (~ 500 °C) magnetite cores with amphibole, pyroxene, and minor Ti–Fe oxide inclusions; type II, an inclusion-free magnetite, usually surrounding type I magnetite cores; type III corresponds to an inclusion-free magnetite with chemical zoning formed under moderate temperatures; and type IV magnetite contains abundant inclusions and is related to low-temperature (~ 250 °C) hydrothermal veinlets. Electron probe and laser ablation ICP-MS analyses of the four magnetite types show that the incorporation of Al, Mn, Ti, and V into the magnetite structure is controlled by temperature. Vanadium and Ga concentrations are relatively constant within each magnetite type, but are statistically different among magnetite types, suggesting that both Elements could be used to discriminate between magmatic and hydrothermal magnetite. However, our results show that the use of Elemental discrimination diagrams should be coupled with detailed textural studies in order to identify superimposed metasomatic events and evaluate the impact of inclusions on the interpretation of microanalytical data. The presence of a distinct textural and chemical variation between magnetite types in Cerro Negro Norte is explained by a transition from high- to low-temperature magmatic-hydrothermal conditions. The microanalytical data of magnetite presented here, coupled with new δ^34S data for pyrite (− 0.5 to + 4.3‰) and U–Pb ages of the diorite (129.6 ± 1.0 Ma), are indicative of a genetic connection between the diorite intrusion and the magnetite mineralization, supporting a magmatic-hydrothermal flotation model to explain the origin of Kiruna-type deposits in the Coastal Cordillera of northern Chile.